Traffic radar system with electronic test signal generation

ABSTRACT

A mobile test unit for verifying an accuracy of vehicle speeds determined by a traffic radar system comprises a test signal generator and a signal mixer. The test signal generator is configured to generate an electronic test signal having a first frequency. The signal mixer is configured to receive the test signal and a radar beam having a second frequency, wherein the radar beam is transmitted from a radar transceiver of a traffic radar system. The signal mixer is further configured to mix the electronic test signal and the radar beam and to generate a mixed signal having frequency components that include the first frequency and the second frequency, wherein the mixed signal is received by the radar transceiver.

RELATED APPLICATIONS

The current patent application is a non-provisional application which claims priority benefit to U.S. Provisional Application No. 62/569,667, entitled “TRAFFIC RADAR SYSTEM WITH MULTIPLE ZONE TARGET DETECTION”, and filed Oct. 9, 2017; U.S. Provisional Application No. 62/569,923, entitled “GPS ASSISTED PATROL SPEED SEARCH FOR DSP TRAFFIC RADAR”, and filed Oct. 9, 2017; and U.S. Provisional Application No. 62/570,446, entitled “TRAFFIC RADAR SYSTEM WITH ELECTRONIC TUNING FORK TEST FEATURE”, and filed Oct. 10, 2017. The earlier-filed provisional applications are hereby incorporated by reference in their entireties into the current application.

BACKGROUND OF THE INVENTION Field of the Invention

Embodiments of the current invention relate to electronic test circuitry to test traffic radar systems.

Description of the Related Art

Traffic radio and ranging (radar) systems that are implemented in law enforcement patrol vehicles typically include at least one radar transceiver that transmits a radar beam (with a transmitter) and receives reflections of the radar beam (with a receiver) as it bounces off target vehicles in a zone. The received reflections of the radar beam are converted to an electronic signal which is processed to determine the speeds of the target vehicles, which may then be displayed on a display. Periodic testing of the traffic radar systems is necessary to verify the accuracy of the determined speeds of target vehicles. Courts have established that a tuning fork test is an acceptable method to provide the verification. The tuning fork test involves utilizing a tuning fork with metal tines to generate an audible sine wave test signal. The test signal is generated in the vicinity of the transceiver at the same time the transmitter is transmitting the radar beam. Both the radar beam and the test signal are received by the receiver which generates the electronic signal that is processed to determine an equivalent target vehicle speed. The physical specifications of the tuning fork, such as the length of the tines, the cross-sectional area of the tines, the material used, the temperature, etc., determine the test signal frequency and thus, the determined equivalent speed. Hence, a tuning fork can be designed to result in a certain equivalent speed determined by the traffic radar system. For example, a tuning fork can be designed to result in a 35 miles per hour (mph) determined equivalent speed by the traffic radar system. If the traffic radar system does not register 35 mph (plus or minus a tolerance), then the software or hardware of the traffic radar system may need to be serviced.

There are numerous drawbacks to using a mechanical tuning fork to verify the accuracy of the traffic radar system. First, the frequency output of the tuning fork varies, in part, with the temperature of the tuning fork. In extreme heat or cold, the frequency output of the tuning fork may be off from its designed output by dozens of Hertz (Hz)—resulting in a false negative determination by the traffic radar system. Second, each tuning fork outputs only a single frequency. So, in order to test the traffic radar system at multiple speeds, a plurality of tuning forks are required. Third, a greater magnitude of the tuning fork output may make the test of the traffic radar system easier to perform. However, the magnitude of the output of the tuning fork is difficult to control since the magnitude varies with the type of surface against which the fork is struck and the force with which it is struck. Fourth, the amount of time that the tuning fork output lasts is limited, possibly requiring the tuning fork to be struck repeatedly to perform the test. Fifth, the frequency output of each tuning fork used to test the traffic radar system at multiple speeds is typically a non-standard frequency that cannot readily be used for other purposes, such as tuning musical instruments. Sixth, there is no communication between the tuning fork and the traffic radar system to automate the testing process. Thus, the operator must start striking the tuning fork once the traffic radar system is ready. And he must check the displayed equivalent speed to determine whether the test was successful or whether it needs to be run again.

SUMMARY OF THE INVENTION

Embodiments of the current invention solve the above-mentioned problems and provide a distinct advance in the art of testing traffic radar systems. Exemplary embodiments provide a mobile test unit that generates an electronic test signal which mixes with a radar beam from the traffic radar system automatically and for as long as necessary to complete the test. The mobile test unit is configured to generate the test signal having one of a plurality of frequencies, with each frequency corresponding to a known equivalent vehicle speed.

The mobile test unit comprises a test signal generator and a signal mixer. The test signal generator is configured to generate the electronic test signal having a first frequency. The signal mixer is configured to receive the test signal and a radar beam having a second frequency, wherein the radar beam is transmitted from a radar transceiver of a traffic radar system. The signal mixer is further configured to mix the electronic test signal and the radar beam and to generate a mixed signal having frequency components that include the first frequency and the second frequency, wherein the mixed signal is received by the radar transceiver.

Another embodiment of the current invention provides a traffic radar system implemented with a law enforcement patrol vehicle. The traffic radar system comprises a first radar transceiver, a second radar transceiver, a mobile test unit, and a processing element. The first radar transceiver is configured to transmit a first radar beam that has a first frequency and receive a mixed signal. The first radar transceiver is further configured to generate a first electronic signal based on the received mixed signal. The second radar transceiver is configured to transmit a second radar beam that has the first frequency and receive the mixed signal. The second radar transceiver is further configured to generate a second electronic signal based on the received mixed signal. The mobile test unit configured to generate the mixed signal having frequency components that include the first frequency and a second frequency. The processing element is configured to receive a plurality of digital data samples derived from the first or second electronic signals, process the digital data samples to process the digital data samples to calculate a frequency component, determine a test speed corresponding to the frequency component, and determine if the test speed is equal to a speed corresponding to the second frequency.

Yet another embodiment of the current invention provides a traffic radar system implemented with a law enforcement patrol vehicle. The traffic radar system comprises a first radar transceiver, a second radar transceiver, a test signal generator, a signal mixer, and a processing element. The first radar transceiver is configured to transmit a first radar beam that has a first frequency and receive a mixed signal. The first radar transceiver is further configured to generate a first electronic signal based on the received mixed signal. The second radar transceiver is configured to transmit a second radar beam that has the first frequency and receive the mixed signal. The second radar transceiver is further configured to generate a second electronic signal based on the received mixed signal. The test signal generator is configured to generate an electronic test signal having a second frequency. The signal mixer is configured to receive the test signal and the first radar beam or the second radar beam. The signal mixer is further configured to mix the electronic test signal and either the first radar beam or the second radar beam and to generate the mixed signal having frequency components that include the first frequency and the second frequency. The processing element is configured to receive a plurality of digital data samples derived from the first or second electronic signals, perform a time domain to frequency domain conversion on the digital data samples to calculate a frequency component, determine a test speed corresponding to the calculated frequency component, and determine if the test speed is equal to a speed corresponding to the second frequency.

This summary is provided to introduce a selection of concepts in a simplified form that are further described below in the detailed description. This summary is not intended to identify key features or essential features of the claimed subject matter, nor is it intended to be used to limit the scope of the claimed subject matter. Other aspects and advantages of the current invention will be apparent from the following detailed description of the embodiments and the accompanying drawing figures.

BRIEF DESCRIPTION OF THE DRAWING FIGURES

Embodiments of the current invention are described in detail below with reference to the attached drawing figures, wherein:

FIG. 1 is a schematic block diagram illustrating electronic components of a traffic radar system, constructed in accordance with various embodiments of the current invention, the traffic radar system including a main unit and a mobile test unit;

FIG. 2 is an environmental top view of a law enforcement patrol vehicle and a target vehicle, the law enforcement patrol vehicle is equipped with the traffic radar system which includes a front radar transceiver generating a first radar beam and a rear radar transceiver generating a second radar beam;

FIG. 3 is a schematic block diagram illustrating electronic components of the front radar transceiver assembly;

FIG. 4 is a schematic block diagram illustrating electronic components of the rear radar transceiver assembly;

FIG. 5 is a schematic block diagram illustrating electronic components of the mobile test unit;

FIG. 6 is a circuit schematic of a signal mixer from the mobile test unit;

FIG. 7 is a first screen capture of at least a portion of a display of the main unit illustrating a test mode for the front radar transceiver;

FIG. 8 is a second screen capture of at least a portion of the display illustrating the test mode for the front radar transceiver;

FIG. 9 is a third screen capture of at least a portion of the display illustrating the test mode for the front radar transceiver;

FIG. 10 is a fourth screen capture of at least a portion of a display illustrating the test mode for the front radar transceiver;

FIG. 11 is a first screen capture of at least a portion of the display illustrating the test mode for the rear radar transceiver;

FIG. 12 is a second screen capture of at least a portion of the display illustrating the test mode for the rear radar transceiver;

FIG. 13 is a third screen capture of at least a portion of the display illustrating the test mode for the rear radar transceiver; and

FIG. 14 is a fourth screen capture of at least a portion of the display illustrating the test mode for the rear radar transceiver.

The drawing figures do not limit the current invention to the specific embodiments disclosed and described herein. The drawings are not necessarily to scale, emphasis instead being placed upon clearly illustrating the principles of the invention.

DETAILED DESCRIPTION OF THE EMBODIMENTS

The following detailed description of the invention references the accompanying drawings that illustrate specific embodiments in which the invention can be practiced. The embodiments are intended to describe aspects of the invention in sufficient detail to enable those skilled in the art to practice the invention. Other embodiments can be utilized and changes can be made without departing from the scope of the present invention. The following detailed description is, therefore, not to be taken in a limiting sense. The scope of the present invention is defined only by the appended claims, along with the full scope of equivalents to which such claims are entitled.

Referring to FIGS. 1 and 2, a traffic radar system 10, constructed in accordance with various embodiments of the current invention, broadly comprises a front radar transceiver 12, a rear radar transceiver 14, a display 16, a switch 18, an analog-to-digital converter (ADC) 20, a communication element 22, a memory element 24, a processing element 26, and a mobile test unit 28. The traffic radar system 10 is typically installed in or on a law enforcement patrol vehicle 30 and is utilized to monitor the speeds of (target) vehicles 32 on a roadway.

The display 16, the switch 18, the ADC 20, the memory element 24, and the processing element 26 generally form a main unit 34. The main unit 34 may include additional components not shown in the figures and not discussed in greater detail. The additional components may include a housing to retain the electronic circuits, a user interface to allow users to operate the system 10, and so forth. The housing may also include a mount or hardware to mount the main unit 34 in or on the vehicle dashboard or center console.

The front radar transceiver 12 generally transmits and receives radio frequency (RF) electromagnetic radiation for a radio detection and ranging (radar) application. The front radar transceiver 12 may include a transmitter 36A, a receiver 38A, and an antenna 40A, as shown in FIG. 3. The transmitter 36A may include electronic signal transmitting circuits, such as oscillators, mixers, frequency multipliers, filters, amplifiers, impedance matchers, and the like. The transmitter 36A generates a first RF electronic signal with an exemplary frequency of approximately 35.5 gigahertz (GHz), which is in the Ka band (33.4 GHz to 36.0 GHz) of radar frequency band classification. The transmitter 36A may receive a signal, command, or data input that triggers it to generates a first RF electronic signal. Or, the transmitter 36A may generate the first RF electronic signal on a regular, periodic basis.

The receiver 38A may include electronic signal receiving circuits, such as oscillators, mixers, matched filters, amplifiers, and the like. The receiver 38A may receive a second RF electronic signal that includes reflection data resulting from reflections of a radar beam off of objects in the vicinity of the front radar transceiver 12. Mixing circuitry of the receiver 38A may remove the radar frequency component of the second RF electronic signal such that the receiver 38 generates a front radar output electronic signal that includes frequency components from the reflection data. In various embodiments, the front radar output electronic signal has a dual complex or quadrature (I/Q) format. The front radar output electronic signal is communicated to the main unit 34.

The antenna 40A generally transmits a first radar beam 42 and receives reflections of the first radar beam 42 as it reflects from target vehicles 32. When the antenna 40A receives the first RF electronic signal from the transmitter 36A, it transmits the first radar beam 42, that is, radio wave electromagnetic radiation forming the radar beam having an exemplary frequency of approximately 35.5 GHz. When the antenna 40A receives reflections of the first radar beam 42, it generates the second RF electronic signal. The antenna 40A may be embodied by directional antennas such as a parabolic antennas. The antenna 40A may transmit the first radar beam 42 as shown in FIG. 2, wherein the first radar beam 42 may have a width of approximately 12 degrees. The front radar transceiver 12 may be mounted or installed on the forward portion of the patrol vehicle, such as a hood, a grill, or a front bumper of the vehicle. Thus, the first radar beam 42 is transmitted in front of the patrol vehicle, also known as the “front zone”.

Referring to FIG. 4, the rear radar transceiver 14 includes a transmitter 36B, a receiver 38B, and an antenna 40B, each of which is substantially identical in structure and function to the like-named components described above for the front radar transceiver 12. After receiving a signal, command, or data input, the transmitter 36B generates a second RF electronic signal. The antenna 40B receives the second RF electronic signal and transmits a corresponding second radar beam 44 as shown in FIG. 2, wherein the second radar beam 44 may also have a width of approximately 12 degrees. The receiver 38B may generate a rear radar output electronic signal that varies according to reflections of the second radar beam 44 received by the antenna 40B. In various embodiments, the rear radar output electronic signal has a dual complex or quadrature (I/Q) format. The rear radar output electronic signal is communicated to the main unit 34. The rear radar transceiver 14 may be mounted or installed on the rear portion of the patrol vehicle, such as a trunk cover or a rear bumper of the vehicle. Thus, the second radar beam 44 is transmitted in the rear of the patrol vehicle, also known as the “rear zone”.

The display 16 may include video devices of the following types: light-emitting diode (LED), organic LED (OLED), Light Emitting Polymer (LEP) or Polymer LED (PLED), liquid crystal display (LCD), thin film transistor (TFT) LCD, LED side-lit or back-lit LCD, plasma, heads-up displays (HUDs), or the like, or combinations thereof. The display 16 may include a screen on which the information is presented, with the screen possessing a square or a rectangular aspect ratio that may be viewed in either a landscape or a portrait mode. In various embodiments, the display 16 may also include a touch screen occupying the entire screen or a portion thereof so that the display 16 functions as part of a user interface. The touch screen may allow the user to interact with the main unit 34 by physically touching, swiping, or gesturing on areas of the screen.

The switch 18 may have a double pole, double throw (DPDT) configuration with a first pair of input contacts, a second pair of input contacts, and a pair of output contacts. The first input contacts are electrically connected to the front radar transceiver 12 and receive the front radar output electronic signal. The second input contacts are electrically connected to the rear radar transceiver 14 and receive the rear radar output electronic signal. The output contacts may be electrically connected to the ADC 20. The switch 18 may operate in one of two modes. In a first mode, the output contacts receive the front radar output electronic signal. In a second mode, the output contacts receive the rear radar output electronic signal. Selection of the mode is controlled by a switch control signal from the processing element 26.

The ADC 20 receives the front radar output electronic signal or the rear radar output electronic signal from the switch 18. The ADC 20 includes electronic circuitry that converts the analog electrical characteristics of the front radar output electronic signal or the rear radar output electronic signal to a corresponding stream of sampled digital data, which includes a plurality of samples, each sample representing a value of the signal. The ADC 20 communicates the sampled digital data stream of the front radar output electronic signal or the rear radar output electronic signal to the memory element 24, the processing element 26, or both.

The communication element 22 generally allows the main unit 34 to communicate with the mobile test unit 28 as well as other electronic devices, external systems, networks, and the like. The communication element 22 may include signal and/or data transmitting and receiving circuits, such as antennas, amplifiers, filters, mixers, oscillators, digital signal processors (DSPs), and the like. The communication element 22 may establish communication wirelessly by utilizing radio frequency (RF) signals and/or data that comply with communication standards such as cellular 2G, 3G, 4G, Voice over Internet Protocol (VoIP), LTE, Voice over LTE (VoLTE) or 5G, Institute of Electrical and Electronics Engineers (IEEE) 802.11 standard such as WiFi, IEEE 802.16 standard such as WiMAX, Bluetooth™, or combinations thereof. In addition, the communication element 22 may utilize communication standards such as ANT, ANT+, Bluetooth™ low energy (BLE), the industrial, scientific, and medical (ISM) band at 2.4 gigahertz (GHz), or the like. Alternatively, or in addition, the communication element 22 may establish communication through connectors or couplers that receive metal conductor wires or cables which are compatible with networking technologies such as ethernet. In certain embodiments, the communication element 22 may also couple with optical fiber cables. The communication element 22 may be in electronic communication with the memory element 24 and the processing element 26.

The memory element 24 may be embodied by devices or components that store data in general, and digital or binary data in particular, and may include exemplary electronic hardware data storage devices or components such as read-only memory (ROM), programmable ROM, erasable programmable ROM, random-access memory (RAM) such as static RAM (SRAM) or dynamic RAM (DRAM), cache memory, hard disks, floppy disks, optical disks, flash memory, thumb drives, universal serial bus (USB) drives, or the like, or combinations thereof. In some embodiments, the memory element 24 may be embedded in, or packaged in the same package as, the processing element 26. The memory element 24 may include, or may constitute, a “computer-readable medium”. The memory element 24 may store the instructions, code, code statements, code segments, software, firmware, programs, applications, apps, services, daemons, or the like that are executed by the processing element 26. The memory element 24 may also store data that is received by the processing element 26 or the device in which the processing element 26 is implemented. The processing element 26 may further store data or intermediate results generated during processing, calculations, and/or computations as well as data or final results after processing, calculations, and/or computations. In addition, the memory element 24 may store settings, data, documents, sound files, photographs, movies, images, databases, and the like.

The processing element 26 may comprise one or more processors. The processing element 26 may include electronic hardware components such as microprocessors (single-core or multi-core), microcontrollers, digital signal processors (DSPs), field-programmable gate arrays (FPGAs), analog and/or digital application-specific integrated circuits (ASICs), or the like, or combinations thereof. The processing element 26 may generally execute, process, or run instructions, code, code segments, code statements, software, firmware, programs, applications, apps, processes, services, daemons, or the like. The processing element 26 may also include hardware components such as registers, finite-state machines, sequential and combinational logic, and other electronic circuits that can perform the functions necessary for the operation of the current invention. In certain embodiments, the processing element 26 may include multiple computational components and functional blocks that are packaged separately but function as a single unit. The processing element 26 may be in electronic communication with the other electronic components through serial or parallel links that include universal busses, address busses, data busses, control lines, and the like. The processing element 26 may be operable, configured, or programmed to perform the following functions by utilizing hardware, software, firmware, or combinations thereof.

The processing element 26 and the memory element 24 receive either a plurality of front radar digital data samples from the ADC 20 or a plurality of rear radar digital data samples from the ADC 20. The processing element 26 outputs the switch control signal at a first level to set the switch 18 in the first mode such that the front radar output electronic signal is input to the ADC 20 for a first period of time. The processing element 26 outputs the switch control signal at a second level to set the switch 18 in the second mode such that the rear radar output electronic signal is input to the ADC 20 for a second period of time. The first and second periods of time may be equal or they may be different. Once the processing element 26 has received a predetermined number of either front or rear radar digital data samples, it processes them to determine a speed or velocity of target vehicles 32 that are in either the front zone or the rear zone, respectively. The data processing may involve converting the front or rear radar digital data samples, which is time-domain data, from the time domain to a frequency domain by utilizing a discrete Fourier transform (DFT), a fast Fourier transform (FFT), or the like. Exemplary embodiments utilize the FFT. Thus, the predetermined number of front or rear radar digital data samples is an amount of samples necessary for the processing element 26 to perform an M-point FFT, where M is a 2^(n) value, such as 256, 512, 1024, etc. The front and rear radar digital data samples may include a plurality of frequency components, each one having a magnitude, that are revealed by the time domain to frequency domain conversion. The frequency components also correspond, or relate, to a speed of a vehicle. Based on the frequency components of the FFT calculation, the processing element 26 determines the speed of each target vehicle 32 that is in either the front zone or the rear zone. The processing element 26 then controls the display 16 to display the speed of one or more target vehicles 32.

The processing element 26 may further receive input from the operator through the user interface of the main unit 34, such as a pushbutton, a keypad key, or an onscreen menu option, requesting to put the traffic radar system 10 in test mode. In some embodiments, the operator may also be able to select the vehicle speeds he wants to simulate. In other embodiments, a plurality of speeds may be automatically selected. Once in test mode, the processing element 26 may transmit, through the communication element 22, a test start command to the mobile test unit 28. The processing element 26 may also transmit a plurality of speeds to be tested.

In addition, the processing element 26 communicates a signal, command, or data to the front radar transceiver 12 to transmit the first radar beam 42. The processing element 26 may instruct the front radar transceiver 12 to transmit the first radar beam 42 until all test speeds have been tested using the front radar transceiver 12. While the first radar beam 42 is transmitted, the front radar transceiver 12 receives RF radiation or signals and outputs the front radar output electronic signal which varies according to the received RF radiation or signals. The ADC 20 digitizes the front radar output electronic signal to produce front radar digital data samples which are received by the processing element 26. The processing element 26 processes the front radar digital data samples, as described above, and determines a test speed. The test speed is either within the tolerance of the expected test speed, which means the test passed, or is not within the tolerance of the expected test speed, meaning the test failed. The processing element 26 stores the result of the speed test in the memory element 24 and may control the display 16 to display the result. The processing element 26 may then instruct the mobile test unit 28 to generate the next frequency to test the next test speed until all the test speeds have been tested. Afterward, the processing element 26 may repeat the same test steps for the rear radar transceiver 14.

While the above-discussed speed tests are performed with the assumption that the patrol vehicle 30 is stationary, which it is, the processing element 26 is further configured to perform the speed tests while simulating that the patrol vehicle 30 is moving. There is an additional step to perform in determining target vehicle speed when the patrol vehicle 30 is moving. The vehicle speed determined from the time domain to frequency domain conversion is a relative speed. An additional calculation is performed depending on the direction in which the target vehicle 32 is traveling relative to the simulated direction of travel of the patrol vehicle 30. For example, when the target vehicle 32 is traveling in the opposite direction from the patrol vehicle 30, the relative vehicle speed is the sum of the actual vehicle speed and the patrol vehicle speed. Thus, the actual target vehicle speed is the absolute value of the difference of the relative vehicle speed and the patrol vehicle speed. When the target vehicle 32 is traveling in the same direction as the patrol vehicle 30, the relative vehicle speed is the absolute value of the difference of the actual vehicle speed and the patrol vehicle speed. Thus, the actual vehicle speed is either the sum of the patrol vehicle speed and the relative vehicle speed or the difference of the patrol vehicle speed and the relative vehicle speed, depending on phase data produced in the time domain to frequency domain conversion. In all situations, in order to determine the actual vehicle speed, the processing element 26 provides a predetermined value for the patrol vehicle speed. The predetermined value may be retrieved from the memory element 24 or may be entered by the law enforcement officer.

The mobile test unit 28 verifies that the other components of the traffic radar system 10 are determining the speeds of the target vehicles 32 accurately. The mobile test unit 28 comprises a communication element 46, a test signal generator 48, a signal mixer 50, and a processing element 52. The mobile test unit 28 also includes a housing, a display, a user interface, and other components not shown in the figures and not discussed in greater detail. The housing of the mobile test unit 28 is sized and shaped such that the mobile test unit 28 fits in a human hand and thus may be easily held, carried, or moved.

The communication element 46 is substantially similar in structure and function to the communication element 22 discussed above. The two communication elements 22, 46 typically allow the main unit 34 and the mobile test unit 28 to communicate with one another wirelessly, although the communication elements 22, 46 may also allow for wired communication through electric cables connecting the main unit 34 and the mobile test unit 28.

The test signal generator 48 generates an electronic test signal or waveform having one of a plurality of frequencies, wherein the frequency is specified by the processing element 26. The test signal generator 48 may include waveform generating electronic circuitry such as crystals, oscillators, multivibrators, amplifiers, filters, or the like, or combinations thereof. To test the traffic radar system 10 at a wide range of vehicle speeds, the test signal generator 48 is configured or operable to generate the test signal having a test frequency broadly ranging from approximately 1,000 Hz to approximately 10,000 Hz. The generated signal, having the specified frequency, is communicated to the signal mixer 50.

The signal mixer 50 receives a first signal having a first frequency and a second signal having a second frequency, mixes the two signals, and generates a third signal having frequency components that include the first frequency and the second frequency. The signal mixer 50 may include electronic circuitry such as diodes, transistors, inductors, or the like, or combinations thereof. An exemplary signal mixer 50 is shown in FIG. 6 and includes resistors R1 and R2, forming a voltage divider network, resistor R3 and capacitor C1, forming a low pass filter, resistor R4, providing an electric current limit, and a silicon mixer Schottky diode D1, which mixes the first signal and the second signal. The signal mixer 50 receives the test signal, having the test frequency, from the test signal generator 48 and either radar beam 42, 44, having a radar frequency, from either the front radar transceiver 12 or the rear radar transceiver 14, mixes the two, and generates a mixed signal, having frequency components including the test frequency and the radar frequency.

The processing element 52 may be similar to the processing element 26 in structure. An example of the processing element 52 may include a PIC24FJ32 series microcontroller from Microchip of Chandler, Ariz. In various embodiments, the processing element 52 may include an embedded memory element. The processing element 52 may be operable, configured, or programmed to perform the following functions by utilizing hardware, software, firmware, or combinations thereof. The processing element 52 receives, through the communication element 46, the test start command, placing the mobile test unit 28 in a test mode, from the processing element 26 of the main unit 34. The processing element 52 may also receive a plurality of speeds to test. Alternatively, the processing element 52 may include a predetermined set of speeds to test. Each speed to be tested corresponds to a frequency component of the radar beam 42, 44 that is received by either the front radar transceiver 12 or the rear radar transceiver 14. Thus, the processing element 52 instructs, communicates a command, or communicates data to the test signal generator 48 to generate the test signal at a predetermined frequency that corresponds to one of the speeds to be tested. The relationship between vehicle speed and frequency for Ka-band radar at 35.5 GHz is 1 mph=105.78 Hz. Thus, to test for vehicle speeds between, for example, 20 mph and 70 mph, the related frequencies range from approximately 2,000 Hz to approximately 7,500 Hz.

The processing element 52 may further receive communication from the main unit 34 indicating when the test of each test speed is complete. Thus, the processing element 52 instructs, communicates a command, or communicates data to the test signal generator 48 to stop generating the test signal at the current frequency. If all test speeds have been tested, then the test is complete. Otherwise, the processing element 52 instructs, communicates a command, or communicates data to the test signal generator 48 to generate the test signal at the next frequency.

The mobile test unit 28 may also operate in a self-test or certification mode so that the test signal output can be verified, by external test equipment, to have the correct, accurate frequency. A service technician may place the mobile test unit 28 in self-test mode through the user interface. The service technician may also select a frequency of the test signal to be generated. The processing element 52 then instructs the test signal generator 48 to generate the test signal. The mobile test unit 28 may include an electronic access point through which external test equipment, such as frequency counters, oscilloscopes, etc., can electronically access the test signal. Alternatively or additionally, the mobile test unit 28 may include a speaker or transducer, which can play the test signal as an audible sound. In such a situation, external test equipment may include a microphone to receive the audible sound. If the frequency of the test signal is not what it should be, then components of the test signal generator 48, such as a crystal, may be inspected, or software or firmware of the processing element 26 and/or test signal generator 48 may be updated.

When it is time to test the traffic radar system 10, the law enforcement officer puts the system 10 in test mode, usually through a pushbutton, a keypad key, or an onscreen menu option on the main unit 34. The law enforcement officer then positions the mobile test unit 28 in proximity to the antenna 40A of the front radar transceiver 12.

The traffic radar system 10 may operate, when in the test mode, as follows. The processing element 26 of the main unit 34 communicates the test start command to the mobile test unit 28. The main unit 34 may begin the test with the front radar transceiver 12. The processing element 26 instructs the front radar transceiver 12 to transmit the first radar beam 42. The processing element 52 of the mobile test unit 28 instructs the test signal generator 48 to generate the test signal. The test signal and the first radar beam 42 are received by the signal mixer, which mixes the test signal and the first radar beam 42 and outputs the mixed signal. The mixed signal (from the mobile test unit 28) is received by the front radar transceiver 12, which effectively removes the radar beam frequency component of the mixed signal, leaving the test signal frequency component. The front radar transceiver 12 communicates the front radar output electronic signal, including the test signal frequency component, to the ADC 20 which digitizes the signal and generates digital data samples. The front radar digital data samples are received by the processing element 26 which processes them and determines a test speed that corresponds to the test signal frequency component. If the determined test speed is within the tolerance of the expected test speed, then the traffic radar system 10 passed the test. If the determined test speed is outside the tolerance of the expected test speed, then the traffic radar system 10 failed the test. The processing element 26 may store the result in the memory element 24 and may control the display 16 to display the result, the expected test speed, and the determined test speed. The processing element 26 of the main unit 34 may instruct the processing element 52 of the mobile test unit 28 to have the test signal generator 48 generate the test signal with a frequency corresponding to the next speed to test. The preceding steps may be repeated until all the speeds have been tested with the front radar transceiver 12.

Referring to FIGS. 7-10, at least a portion of the display 16 of the main unit 34 is shown at different stages during the test mode for the front radar transceiver 12. The display 16 may include a first indicia 54 positioned on the left side of the display 16, a second indicia 56 positioned on the right side of the display 16, and a third indicia 58 positioned in the center of the display 16. The first indicia 54 and the second indicia 56 may indicate what type of test is being conducted (low “Lo” speed or high “Hi” speed), the results of the test (“PAS” for pass or “err” for fail, which is not shown in the figures), or the determined equivalent speed. For these exemplary test, the low speed is 35 mph and the high speed is 65 mph. In addition, the first indicia 54 and the second indicia 56 are positioned closer to the upper edge of the display 16 and have a first specific color, e.g., red, both to indicate that the front radar transceiver 12 is being tested. The third indicia 58 may indicate the results of the test, or the determined equivalent speed. The display 16 may further include a front indicator 60, indicating the front radar transceiver 12 is in use, a vehicle icon 62, indicating the position of a potential target vehicle 32 relative to the patrol vehicle 30 (in this case, that the potential target vehicle 32 is in front of the patrol vehicle 30 traveling the opposite direction), and a test indicator 64, indicating the traffic radar system 10 is in the test mode. FIG. 7 illustrates the display 16 when the traffic radar system 10 has just entered the test mode. FIG. 8 illustrates the display 16 when the traffic radar system 10 has passed the low speed test. FIG. 9 illustrates the display 16 when the traffic radar system 10 has passed the high speed test.

FIG. 10 illustrates the display 16 when the two speed tests are over. The first indicia 54 indicates the results of the two tests combined. If both tests passed, then the first indicia 54 displays a passing result. While if either speed test failed, then the first indicia 54 indicates a failing result. FIG. 10 also illustrates the results of running the speed test when a non-zero speed of the patrol vehicle 30 is simulated, that is, to simulate when the patrol vehicle is moving. When performing this type of test, the equivalent vehicle speed is displayed in the second indicia 54. In the example of FIG. 10, the relative determined vehicle speed is 65 mph (which is not displayed), and the patrol vehicle speed is simulated to be 35 mph. Since the vehicle icon 62 indicates that the target vehicle 32 is traveling in the opposite direction from the patrol vehicle 30, the relative vehicle speed is the sum of the actual vehicle speed and the patrol vehicle speed. Thus, the actual target vehicle speed is the absolute value of the difference of the relative vehicle speed and the patrol vehicle speed—which in this example is 30 mph.

Referring to FIGS. 11-14, at least a portion of the display 16 of the main unit 34 is shown at different stages during the test mode for the rear radar transceiver 14. When testing the rear radar transceiver 14, the first indicia 54 and the second indicia 56 are positioned closer to the lower edge of the display 16 and have a second specific color, e.g., blue, both to indicate that the rear radar transceiver 14 is being tested. The vehicle icon 62 is positioned to indicate that the potential target vehicle 32 is behind the patrol vehicle 30 traveling the same direction. The display 16 may further include a rear indicator 66, indicating the rear radar transceiver 14 is in use. FIG. 11 illustrates the display 16 when the traffic radar system 10 has just entered the test mode. FIG. 12 illustrates the display 16 when the traffic radar system 10 has passed the high speed test. FIG. 13 illustrates the display 16 when the traffic radar system 10 has passed the low speed test.

FIG. 14 illustrates the display 16 when the two speed tests are over. As with FIG. 10 discussed above, the first indicia 54 indicates the results of the two tests combined. If both tests passed, then the first indicia 54 displays a passing result. While if either speed test failed, then the first indicia 54 indicates a failing result. FIG. 14 also illustrates the results of running the speed test when a non-zero speed of the patrol vehicle 30 is simulated. Since the vehicle icon 62 indicates that the target vehicle 32 is traveling in the same direction as the patrol vehicle 30, the relative vehicle speed is the absolute value of the difference of the actual vehicle speed and the patrol vehicle speed. Thus, the actual vehicle speed is either the sum of the patrol vehicle speed and the relative vehicle speed or the difference of the patrol vehicle speed and the relative vehicle speed, depending on phase data produced in the time domain to frequency domain conversion. In the example, of FIG. 14, the relative vehicle speed is 35 mph, the patrol vehicle speed is 65 mph, and the actual vehicle speed is 100 mph.

After the testing of the front radar transceiver 12 is complete, the main unit 34, the mobile test unit 28, or both may indicate to the law enforcement officer to position the mobile test unit 28 in proximity to the antenna 40B of the rear radar transceiver 14. The testing process described in the previous paragraph may be repeated for the rear radar transceiver 14. The results of the individual vehicle speed tests for the rear radar transceiver 14 may be stored in the memory element 24 and displayed on the display 16.

In various embodiments, it may be possible for the mobile test unit 28 to be utilized when the main unit 34 is not in the test mode. The main unit 34 may be operating in one of its normal modes—instructing the front radar transceiver 12 to transmit the first radar beam 42 or the rear radar transceiver 14 to transmit the second radar beam 44. The main unit 34 may also process the data derived from signals from either the front radar transceiver 12 or the rear radar transceiver 14 to determine vehicle speeds based on reflections of the radar beams 42, 44. The mobile test unit 28 may be placed in the test mode manually so that the test signal generator 48 generates the test signal. With the mobile test unit 28 positioned in proximity to the antenna 40 of the active radar transceiver 12, 14, the active radar transceiver 12, 14 receives the mixed signal and the processing element 26 processes the front or rear radar digital data samples, as described above, to determine and an equivalent speed. The processing element 26 may also control the display 16 to display the speed. The law enforcement officer may then view the displayed speed to determine whether it is within the tolerance of the expected speed.

Although the invention has been described with reference to the embodiments illustrated in the attached drawing figures, it is noted that equivalents may be employed and substitutions made herein without departing from the scope of the invention as recited in the claims.

Having thus described various embodiments of the invention, what is claimed as new and desired to be protected by Letters Patent includes the following: 

1. A mobile test unit for verifying an accuracy of vehicle speeds determined by a traffic radar system, the mobile test unit comprising: a test signal generator configured to generate an electronic test signal having a first frequency; and a signal mixer configured to receive the test signal and a radar beam having a second frequency, the radar beam transmitted from a radar transceiver of a traffic radar system, the signal mixer further configured to mix the electronic test signal and the radar beam and to generate a mixed signal having frequency components that include the first frequency and the second frequency, the mixed signal received by the radar transceiver.
 2. The mobile test unit of claim 1, wherein the first frequency has a range from approximately 1,000 Hertz to approximately 10,000 Hertz.
 3. The mobile test unit of claim 1, wherein the first frequency corresponds to a vehicle speed to be tested.
 4. The mobile test unit of claim 1, wherein the second frequency is in the Ka band of frequencies.
 5. The mobile test unit of claim 1, wherein the signal mixer includes a diode configured to receive the test signal and the radar beam and to generate the mixed signal.
 6. A traffic radar system implemented with a law enforcement patrol vehicle, the traffic radar system comprising: a first radar transceiver configured to transmit a first radar beam that has a first frequency and receive a mixed signal, the first radar transceiver further configured to generate a first electronic signal based on the received mixed signal; a second radar transceiver configured to transmit a second radar beam that has the first frequency and receive the mixed signal, the second radar transceiver further configured to generate a second electronic signal based on the received mixed signal; a mobile test unit configured to generate the mixed signal having frequency components that include the first frequency and a second frequency; and a processing element configured to receive a plurality of digital data samples derived from the first or second electronic signals, process the digital data samples to calculate a frequency component, determine a test speed corresponding to the frequency component, and determine if the test speed is equal to a speed corresponding to the second frequency.
 7. The traffic radar system of claim 6, wherein the processing element is further configured to perform a time domain to frequency domain conversion on the digital data samples to calculate the frequency component.
 8. The traffic radar system of claim 6, wherein the processing element is further configured to simulate that the patrol vehicle is moving, determine the test speed as a relative test speed, and convert the relative test speed to an absolute test speed using a predetermined value of a speed of the patrol vehicle.
 9. The traffic radar system of claim 8, wherein the processing element is further configured to convert the relative test speed to the absolute test speed using addition or subtraction depending upon a direction of travel of a simulated target vehicle relative to a simulated direction of travel of the patrol vehicle.
 10. The traffic radar system of claim 6, wherein the first radar transceiver is further configured to generate the first electronic signal to have frequency components excluding the first frequency.
 11. The traffic radar system of claim 6, wherein the second radar transceiver is further configured to generate the second electronic signal to have frequency components excluding the first frequency.
 12. The traffic radar system of claim 6, wherein the mobile test unit includes a test signal generator configured to generate an electronic test signal having the second frequency.
 13. The traffic radar system of claim 12, wherein the mobile test unit includes a signal mixer configured to receive the test signal and the first radar beam or the second radar beam, the signal mixer further configured to mix the electronic test signal and either the first radar beam or the second radar beam and to generate the mixed signal.
 14. The traffic radar system of claim 6, further comprising an analog to digital converter configured to receive the first electronic signal and the second electronic signal and output a plurality of front radar digital data samples and a plurality of rear radar digital samples.
 15. A traffic radar system implemented with a law enforcement patrol vehicle, the traffic radar system comprising: a first radar transceiver configured to transmit a first radar beam that has a first frequency and receive a mixed signal, the first radar transceiver further configured to generate a first electronic signal based on the received mixed signal; a second radar transceiver configured to transmit a second radar beam that has the first frequency and receive the mixed signal, the second radar transceiver further configured to generate a second electronic signal based on the received mixed signal; a test signal generator configured to generate an electronic test signal having a second frequency; a signal mixer configured to receive the test signal and the first radar beam or the second radar beam, the signal mixer further configured to mix the electronic test signal and either the first radar beam or the second radar beam and to generate the mixed signal having frequency components that include the first frequency and the second frequency; and a processing element configured to receive a plurality of digital data samples derived from the first or second electronic signals, perform a time domain to frequency domain conversion on the digital data samples to calculate a frequency component, determine a test speed corresponding to the calculated frequency component, and determine if the test speed is equal to a speed corresponding to the second frequency.
 16. The traffic radar system of claim 15, wherein the first radar transceiver is further configured to generate the first electronic signal to have frequency components excluding the first frequency.
 17. The traffic radar system of claim 15, wherein the second radar transceiver is further configured to generate the second electronic signal to have frequency components excluding the first frequency.
 18. The traffic radar system of claim 15, further comprising an analog to digital converter configured to receive the first electronic signal and the second electronic signal and output a plurality of front radar digital data samples and a plurality of rear radar digital samples.
 19. The traffic radar system of claim 15, wherein the processing element is further configured to simulate that the patrol vehicle is moving, determine the test speed as a relative test speed, and convert the relative test speed to an absolute test speed using a predetermined value of a speed of the patrol vehicle.
 20. The traffic radar system of claim 19, wherein the processing element is further configured to convert the relative test speed to the absolute test speed using addition or subtraction depending upon a direction of travel of a simulated target vehicle relative to a simulated direction of travel of the patrol vehicle. 